Evaluation of Rubblization Techniques Over Soft Soils
I. Problem Statement:
Various states have adopted Rubblization in their pavement sections however some of these sections have performed poorly when constructed over soft soils. Various states need to modify their construction methods to account for the soft soils within the pavement structure. In Wisconsin, in areas where poor subgrade was a problem, the speed of the machine was increased to minimize the energy delivered into the pavement during rubblization. The reduction in energy per area of rubblized pavement due to the increased speed of the rubblization machine results in larger 15 to 20 mm pieces of concrete. The quality of the crushed stone was pretty consistent. In places where the pieces were considered too big the machine was slowed down again to meet specifications. Speed was varied based on quality of the concrete and the resulting diameter of the aggregate. After being rubblized, the crushed concrete comprised of particles larger than the requisite 5 cm diameter pieces and the concrete was seated with one or two passes with a vibratory grid roller. Then a rubber roller was used to compact any uneven areas left by the grid roller. The grid roller tends to bridge some areas, and the rubber roller gets in those grooves. Finally, a steel-wheel roller was used to eliminate any unevenness [RAT 00]. The rubblized section is performing well three years after construction.
In Iowa, a 3.0 km (1.9 mi) section of L63 in Mills County was rubblized using a resonant frequency vibration pavement breaker. The main findings were that the presence of edge drains was found to improve the structural rating of the rubblized roadway. The drains provided good drainage to the base and kept it stable [TYM 95]. Similarly, experience in Colorado with rubblization over soft soils has resulted in edge drains being recommended in conjunction with rubblization as a to control subgrade moisture. The Colorado Department of Transportation has found that edge drains worked extremely well in getting excess water out of the pavement system [DON 00]. In Michigan, a study clearly showed that the provision of sufficient drainage and thickness of overlay will lead to durable pavements and that, for certain concrete pavements, rubblization is not a viable option because it may lead to inadequate pavement performance [NIE 00], [GAL 99]. Thus, several state agencies have had success with rubblization over soft soils by providing edge drains, modifying rubblization techniques, and providing sufficient overlay thicknesses.
Some of the modifications to construction include:
1. Edge drains should be installed to provide adequate drainage.
2. Allowing sufficient time for pore water to dissipate and drain through the edge may help in reducing pore pressure. This means that a geotechnical evaluation for excess pore pressures to dissipate in underlying layers should be performed prior to construction.
3. Rubblization may not be suitable over soft soils with high water table and other options of rehabilitation like crack and seat should be considered.
II. Research Objective:
The objective of this research is to recommend rubblization techniques over soft soils.
III. Proposed Scope of Work
Accomplishment of this objective will require at least the following tasks that are grouped into two separate phases.
Phase I – Evaluate Current Rubblization Techniques
(1) In addition to the method used by MnDOT and KDOT and the research performed by URI and KSU, collect and review other relevant domestic and foreign literature, research findings, performance data, current practices, and other information relative to the use, testing, and evaluation of partial-depth CIR. This information may be obtained from published and unpublished reports, contacts with transportation agencies and industry organizations, and other sources. The literature review should note distresses that are observed with this rehabilitation strategy.
(2) Identify the performance parameters of the CIR layer that are important to short and long-term performance and develop new procedures or modifications of current test procedures for measuring those performance-related properties. The simple performance tests from NCHRP 9-19 and the material property inputs required by the 2002 Design Guide should be reviewed and evaluated.
(3) Prepare an updated, detailed work plan for Phase II that includes an experimental plan to evaluate and validate the most promising procedures for measuring CIR properties that relate to pavement performance. A detailed, statistically but practical experimental plan should be developed as a part of this task. The experimental plan should identify those test sections or projects that are to be included in Phase II.
(4) Prepare an interim report that documents the research performed in Phase I and includes the updated work plan for Phase II. Following review of the interim report by the sponsor, the research team will be required to make a presentation to the project panel. Work on Phase II of the project will not begin until the interim report is approved and the Phase II work plan is authorized by the sponsor.
Phase II – Develop Modifications to Rubblization Techniques Over soft soils
(5)Execute the plan approved in Task 5. Based on the results of this work, recommend sets of tests for evaluating CIR used in pavement layers. Also, recommend criteria for interpreting test results and assessing CIR acceptability for use in pavement layers.
(6) Determine the ability to use the procedures developed for determining CIR-layer structural coefficients that are required inputs for the 1993 AASHTO Design Guide and the mixture properties that are required by the 2002 Design Guide. A library of mixture properties should be developed to be used on a national basis with the 2002 Design Guide, especially if that Guide is adopted by AASHTO for future use in designing flexible pavement structures.
(7)Submit a final report that documents the entire research effort. The report shall include an implementation plan for moving the results of this research into practice.
IV. Literature Search Summary:
[BUS 85] BUSH III A. J., Alexander R. J., “Pavement Evaluation Using Deflection Basin Measurements and Layered Theory”, Transportation Research Record No. 1022, TRB National Research Council, Washington DC, 1985.
[DON 00] DONNA H., WERNER H., JEFF V., “Interstate Asphalt Demonstration Project NH 0762-038 (Rubblization)”, CDOT Region 4. May 2000.
[GAL 99] GALAL K. A., COREE B. J., HADDOCK J. E., WHITE T. D., “Structural Adequacy of Rubblized Portland Cement Concrete Pavement”, Transportation Research Record, 1684, National Research Council, Washington DC, 1999.
[GRA 00] Memorandum from GRAVES AUBREY to Greg Schiess, January 21, 2000.
[HAL 95] HALL K. T., DARTER M., AND CARPENTER S., “Rehabilitation of Asphalt-Overlaid Concrete Pavements”, Final Report, June 1995.
[KSA 99] KSAIBATI K, MILEY W., ARMAGHANI J. “Rubblization of Concrete Pavements”, Transportation Research Record no.1684, National Research Council, Washington DC, pp. 165-171. 1999.
[KUE 91] KUENNEN, T., “Resonant Rubblizing puts Asphalt Over Concrete”, Roads and Bridges, Vol. 29, I-1, 1991.
[NIE 00] NIEDERQUELL M. G; BALADI G. Y., CHATTI K., “Rubblization of Concrete Pavements: Field Investigation”, Transportation Research Record 1730, National Research Council, Washington DC, pp. 150-160. 2000.
[PCC 91] “PCC Rubblizing Project, Overlay Grabs Top Honors”, In Roads and Bridges Vol. 29, I 5, 1991.
[RAD 92] RADA, G. R., WITCZAK. M. W. “Nationwide Evaluation Study of Asphalt Concrete Overlays Placed on Fractured Portland cement Concrete Pavements”, Transportation Research Record 1374, TRB, National Research Council, Washington D.C., 1992.
[RAT 00] RATHMANN. C., “A Recipe For Rubblization”, Roads and Bridges Volume: 38 Issue: 1, Jan 2000.
[ROS 00] ROSENBERGER, C. E., STAPLER W. T, AND VILLACRES J. N. “Use of Rubblization Expands”, Asphalt Magazine, Vol. 25, I-1, pp. 14-15, 2000.
[THO 97] THOMPSON M. R, VAN MATRE F. R., LIPPERT D., JENKINS P., “HMA Overlay Construction With One Pass/Lane Width PCCP Rubblization”, HMAT, Volume: 2 Issue: 1, pp. 21-27, 1997.
[THO 99] THOMPSON M. R., “Hot-Mix Asphalt Overlay Design Concepts For Rubblized Portland Cement Concrete Pavements”, Transportation Research Record 1684, National Research Council, Washington DC, pp. 147-155, 1999.
[TYM 95] TYMKOWICZ S., DEVRIES S., “Iowa Development Of Rubblized Concrete Pavement Base - Mills County”. Final Report, Report Number HR-315 Iowa Department of Transportation, January 1995.
[WAS 95] “Pavement Analysis Software and Case Studies”, WISDOT Pavement Guide Vol. 3, Washington State Department of Transportation, , 1995.
[WIS 00]. How WisDOT Uses Rubblization? Better Roads, February 2000.
[WIT 92] WITCZAK M. W., RADA G. R., “Asphalt Concrete Overlay Design Methodology for Fractured PCC Pavements”, Transportation Research Record 1374, TRB, National Research Council, Washington D.C., 1992.